Peritoneal Dialysis (PD) periodically infuses sterile aqueous solution into the peritoneal cavity. This solution is called peritoneal dialysis solution, or dialysate. Diffusion and osmosis exchanges take place between the solution and the bloodstream across the natural body membranes. These exchanges remove the waste products that the kidneys normally excrete. The waste products typically consist of solutes like sodium and chloride ions, and the other compounds normally excreted through the kidneys like urea, creatinine, and water.
Automated Peritoneal Dialysis (APD) is a popular form of PD. APD uses a machine, called a cycler, to automatically infuse, dwell, and drain peritoneal dialysis solution, or dialysate, to and from the patient's peritoneal cavity. A typical APD sequence lasts for several hours. It often begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate. The APD sequence then proceeds through a succession of fill, dwell, and drain phases that follow one after the other. Each fill/dwell/drain sequence is called a cycle. During the fill phase, the cycler transfers a predetermined volume of fresh, warmed dialysate into the peritoneal cavity of the patient. The dialysate remains (or “dwells”) within the peritoneal cavity for a time. This is called the dwell phase. During the drain phase, the cycler removes the spent dialysate from the peritoneal cavity. The number of fill/dwell/drain cycles that are required during a given APD session depends upon the total volume of dialysate prescribed for the patient's APD regime.
Systems for performing peritoneal dialysis are known in the art. U.S. Pat. No. 5,350,357, entitled Peritoneal Dialysis Systems Employing a Liquid Distribution and Pumping Cassette that Emulates Gravity, and other patents, describe a cassette-based peritoneal dialysis system. PD systems of the type described in U.S. Pat. No. 5,350,357 have been very well received by professionals and patients for the treatment of end-stage renal disease.
Despite the success of such peritoneal dialysis systems, there is a need for sensor apparatus and sensor apparatus systems capable of sensing the temperature, the conductivity, and/or other properties of the dialysate present in the cassette.
Additionally, there is a need for an accurate measurement apparatus to measure the temperature, conductivity, and/or other property of the dialysate in the cassette while avoiding contamination between with the measurement apparatus and the dialysate. There is also a need for an accurate measurement apparatus that can measure the temperature, conductivity, and/or other condition of a dialysate where such dialysate is contained in and/or flowing through a disposable cassette such that part or all of the sensor apparatus can be reused and need not be disposed of along with the disposable cassette.